Neutron Absorbing Concrete Wall and Method for Producing Such Concrete Wall

ABSTRACT

The object of the invention relates to a neutron absorbing concrete wall ( 10 ), which concrete wall ( 10 ) has an internal delimiting surface ( 11   a ), and an external delimiting surface ( 11   b ) on an opposite side to the internal delimiting surface ( 11   a ), the essence of which is that it contains a first concrete layer ( 13   a ) on the side of the internal delimiting surface ( 11   a ), and a second concrete layer ( 13   b ) on the side of the external delimiting surface ( 11   b ), which first concrete layer ( 13   a ) contains at least 0.05 mass % boron-10 isotope ( 10 B), and the second concrete layer ( 13   b ) is formed as heavyweight concrete. The object of the invention also relates to a method for creating a neutron radiation absorbing concrete wall ( 10 ) that has an internal delimiting surface ( 11   a ), and an external delimiting surface ( 11   b ) on an opposite side to the internal delimiting surface ( 11   a ), the essence of which is a first concrete layer ( 13   a ) containing at least 0.05 mass % boron-10 isotope ( 10 B) is formed on the side of the internal delimiting surface ( 11   a ), and a second concrete layer ( 13   b ) created as heavyweight concrete is formed on the side of the external delimiting surface ( 11   b ). The object of the invention also relates to a neutron absorbing concrete wall ( 10 ), the essence of which is that it is formed as heavyweight concrete containing at least 0.05 mass % boron-10 isotope ( 10 B).

The object of the invention relates to a neutron absorbing concretewall, which concrete wall has an internal delimiting surface, and anexternal delimiting surface on an opposite side to the internaldelimiting surface.

The object of the invention also relates to a method for creating aneutron radiation absorbing concrete wall that has an internaldelimiting surface, and an external delimiting surface on an oppositeside to the internal delimiting surface.

Neutron beams have a broad range of applications in various fields ofscience, technology and healthcare. It is necessary to take theappropriate protection measures against the neutrons unavoidably emittedin work with neutron radiation, or during the operation of acceleratorsso that the level of radiation the personnel is exposed to does notreach the level that is harmful to health. A conventional form ofradiation protection is represented by closed, more or less thick walledchambers around the radiation source, the walls of which only permit theneutron radiation present on one side of the walls to pass through tothe other side after being intensively weakened.

As the types of radiation and their effects are many, inhibiting them ispresently carried out with various types of device. In order to provideprotection against neutrons of varying energy, walls have to be providedcontaining various elements so that the required thickness is notextreme.

In the low energy range (e.g. thermal neutrons) several chemicalelements are known that absorb neutrons and are less activated in thisprocess. Examples of such elements include boron, gadolinium or cadmium.However, these substances emit other ionising radiation (e.g.γ-radiation) immediately following the absorption of neutrons, whichalso has to be weakened for protection. In the case of medium-energyneutrons substances containing hydrogen are very effective, which slowdown the neutrons and absorb them to a lower degree. An example of sucha substance is water.

High-energy neutrons are absorbed with high-density and high atomicweight substances. Due to its price and workability iron is used mostoften for this purpose, less often lead. On their own, these materialsare only used when the radiation source is compact, and so a smallvolume needs to be isolated. In practice, however, as a result of theextensive size of the radiation source, it is customary to isolate itwith a concrete structure. Radiation shielding made from concretecustomarily used in the construction industry in many cases can only beachieved with exaggerated structural dimensions. Where the amount ofspace available is limited or valuable and the customary concreteprotection would require too much space, high-density concrete with aspecial composition, so-called heavyweight concrete, is also used which,apart from the traditional components of concrete, contains iron (e.g.iron ore aggregate, iron ore powder, compounds containing iron, or steelshot, etc.), as well as other heavy elements, e.g. barium, lead orcopper. The density of heavyweight concrete is usually between 3200 and5000 kg/m³. The concrete also contributes to the blocking of theneutrons due to its water content.

The problem with radiation shields made from concrete is that the heavyelement components (iron, for example), especially those located closerto the radiation source, become activated due to the effect of the highintensity neutron radiation, especially the low energy neutrons, as aresult of which they emit secondary γ-radiation for an extended period.The radiation of the concrete wall makes any repairs or maintenance tobe performed in the space surrounded by it difficult or even impossible.In addition, the activation of certain activated elements dissipatesonly after a long amount of time (even years), for example, in the caseof iron the dominating half-life is 8 months (as well as shorterduration activated components).

A solution is disclosed in American patent number U.S. Pat. No.3,453,160 that partially overcomes the above problem. The internalsurface of the concrete wall surrounding the radiation source is coveredwith plasterboard sheets impregnated with boric acid, which reduce theactivation of the concrete underneath them. The disadvantage of thesolution is that plasterboard sheets do not contribute to the structuralstability of the structure, in other words they do not fulfil aload-bearing function, while they take up useful space from the enclosedinterior. In addition, it is difficult or even impossible to covercomplex surface (e.g. curves, corners) in this manner. Anotherdisadvantage of the solution is that the elements for securing theplasterboard sheets to the concrete (bolts, anchors) may weaken thestructure of the concrete, and start the formation of cracks in it thatmay represent a safety risk.

German patent document number DE102004063185 discloses a radiationshielding wall structure. In the case of the solution presented thebasis of the radiation shielding consists of blocks made of gypsum thatare placed on one another in such a way that they may be subsequentlydismantled. Optionally, the gypsum blocks contain further layers in asandwich structure. Paragraph 26 of the specification of the documentmentions that a neutron absorbing material, such as boron, can be mixedwith the gypsum, although nothing at all is stated about theconcentration of the additive. A disadvantage of the presented solutionis that complex surfaces (e.g. curves, corners) cannot be constructedfrom the gypsum blocks at all. A further disadvantage of the disclosedsolution is that the loadbearing characteristics of gypsum are wellbelow those of concrete; therefore a wall made from the describedtechnology will be very thick.

American patent application number US2013051512 presents neutronabsorbing components (such as rods used in reactors), however, it doesnot deal with radiation shielding walls.

Korean patent application number KR20160066377 presents a two-layerradiation shielding concrete wall, on the side of which facing theradiation source a concrete layer containing a polymer, and on the otherside a concrete layer containing boron is provided. The two concretelayers are secured to each other forming a sandwich-like concrete wall.An important difference is that here the concrete layer containing boronis not on the side facing the radiation source, also it is important tohighlight that the disclosed solution does not contain any heavyweightconcrete layer. The document mentioned also fails to display therecognition that the heavy element components in the heavyweightconcrete become activated due to the effect of the high intensityneutron radiation.

We recognised that at present a neutron shielding wall that equallyeffectively absorbs low, medium and high energy neutrons and hassuitable load-bearing characteristics and low construction costs doesnot exist.

It was recognised that if 0.05 mass % boron-10 is evenly added toheavyweight concrete a concrete wall can be created that is capable ofabsorbing a wide energy spectrum of neutron radiation.

Furthermore, the invention is based on the recognition that by buildinga heavyweight concrete layer effective at blocking fast neutrons and aconcrete layer containing at least 0.05 mass % boron-10 (¹⁰B) togetheras one, particularly preferably forming them as a single block, a highload-bearing radiation shielding wall may be created that equallyeffectively capable of absorbing low, medium and high energy neutrons.As the boron-10 isotope does not in practice become activated whileabsorbing neutrons, and as the boron-10 isotope absorbs especially thelow energy neutrons with a greater effect cross-section, only a smallerproportion of the neutrons penetrating the concrete wall are absorbed bythe iron, which means that it is less activated during the absorptionprocess.

It was also recognised that the use of a concrete layer containing theboron-10 isotope can effectively reduce not only the activation of theheavyweight concrete but also the propagation of γ-radiation generatedby the activation towards the surrounded internal space.

It was also recognised that the heavy elements (such as iron) and theboron-10 isotope mixed into the heavyweight concrete and responsible forabsorbing the neutron radiation reduce the bonding strength of thecement, which is disadvantageous from the point of view of structuralstability. It was recognised that the above disadvantageous effect maybe overcome, or at least reduced, if the boron-10 isotope is present inthe first concrete layer in uneven concentration, but it is at a maximumat the internal surface facing the radiation source, and minimal, oroptionally zero, on the side facing the heavyweight concrete.

It was also recognised that the concentration gradient of the boron-10isotope mentioned above does not only improve the structuralcharacteristics of the concrete wall, but through this the neutronabsorbing ability of the concrete wall may be increased, and theactivation of the heavyweight concrete can also be more effectivelyreduced. In this way less neutron absorbing material (e.g. iron, steelshot, boron-10 isotope) needs to be added overall to achieve the sameneutron absorbing effect.

The objective of the invention is to provide a device and method that isfree of the disadvantages according to the state of the art. Theobjective is especially to provide a solution with which all componentsof wide energy distribution neutron radiation can be effectively blockedthat can be simply produced at a low cost and with large structuralstrength.

The objects of the invention are achieved with a concrete wall accordingto claims 1 and 15, and a method according to claim 9.

The concrete wall and the method according to the invention are suitablefor multiple uses in connection with low output neutron sources andmedium output neutron sources for research purposes.

According to a further aspect of the invention, it is aimed at providinga method with which a concrete wall with the above characteristics, withan internal delimiting surface and an external delimiting surface on theopposite side to the internal surface can be effectively produced at lowcost.

The task set is solved by providing heavyweight concrete containing atleast 0.05 mass % boron-10 isotope.

The task set is solved by that in the case of the solution according tothe invention a first concrete layer containing at least 0.05 mass %boron-10 isotope is provided on the side of the internal delimitingsurface, and a second concrete layer created as heavyweight concrete isprovided on the side of the external delimiting surface.

According to a particularly preferred embodiment liquid phaseheavyweight concrete is filled into the lower part of a casting mouldfor casting concrete, then liquid phase concrete containing at least0.05 mass % boron-10 isotope is poured into the casting mould onto thetop of the liquid phase heavyweight concrete. In the case of anotherpreferred embodiment liquid phase concrete containing at least 0.05 mass% boron-10 isotope is poured into the lower part of the casting mould,then liquid phase heavyweight concrete is poured onto the top of theliquid phase concrete containing at least 0.05 mass % boron-10 isotope.In the above ways, after the concrete has bonded a second concrete layeris formed from the liquid phase heavyweight concrete and a firstconcrete layer is formed from the liquid phase concrete containing atleast 0.05 mass % boron-10 isotope. Through this a concrete wall may becreated from a single block, the structural strength of which is highand its neutron absorbing ability exceeds that of the solutionsaccording to the state of the art and which is also less prone toactivation.

In the case of another preferred embodiment the liquid phase concretecontaining at least 0.05 mass % boron-10 isotope, or the liquid phaseheavyweight concrete is only poured onto the top of the liquid phaseheavyweight concrete or onto the top of the liquid phase concretecontaining at least 0.05 mass % boron-10 isotope after it has partiallybonded.

Further preferred embodiments of the invention are defined in thedependent claims.

Further details of the invention will be explained by way of exemplaryembodiments with reference to figures, wherein:

FIG. 1 shows a schematic side cross-sectional view of a first exemplaryembodiment of a concrete wall according to the invention,

FIG. 2 shows a schematic side cross-sectional view of a second exemplaryembodiment of a concrete wall according to the invention,

FIG. 3 shows a schematic side cross-sectional view of a third exemplaryembodiment of a concrete wall according to the invention,

FIG. 4a shows a schematic view presenting a state of the production ofthe concrete wall shown in FIG. 1,

FIG. 4b shows a schematic view of a next state of the production of theconcrete wall shown in FIG. 1,

FIG. 5a shows a schematic view of a state of the production of theconcrete wall shown in FIG. 2,

FIG. 5b shows a schematic view of a next state of the production of theconcrete wall shown in FIG. 2.

FIG. 1 shows a schematic side cross-section view of a first exemplaryembodiment of a concrete wall 10 according to the invention. Theconcrete wall is for weakening or absorbing the particle radiation,especially the neutron radiation unavoidably emitted during theoperation of the radiation source 12 (e.g. particle accelerator, such asproton accelerator, or neutron source). The concrete wall 10 delimits aclosed internal volume (radiation volume) containing the radiationsource 12 emitting the neutron radiation. The concrete wall 10 has aninternal delimiting surface 11 a facing the radiation source 12, and anexternal delimiting surface 11 b on the side, facing the outside world,opposite to the internal delimiting surface 11 a. The shape of thesurfaces 11 a, 11 b may be planar, curved, arched, undulating, etc.,according to the volume to be delimited and the type of radiation source12. It should be noted that, optionally, an embodiment is conceivable inthe case of which the radiation volume is enclosed with a single,continuous, for example, dome shaped concrete wall 10, but an embodimentmay be conceived in the case of which the closed internal volume iscreated by securing several concrete wall 10 elements (e.g. with arectangular surface 11 a) to each other, similarly to the internal spaceof a room.

The concrete wall 10 contains a first concrete layer 13 a on the side ofthe internal delimiting surface 11 a, and a second concrete layer 13 bon the side of the external delimiting surface 11 b. In the case of thepreferred embodiment shown in FIG. 1, the concrete wall 10 is formed asa single block, in other words as a single jointly cast block includingthe first and second concrete layers 13 a, 13 b. In this case theconcrete layers 13 a, 13 b are secured to each other by the hydraulicbonding occurring with the solidification of the cement in them, theconcrete layers 13 a, 13 b are not physically separated from each other.The imaginary layer border 14 separating the concrete layers 13 a, 13 bhas been included for illustration purposes.

In the case of the concrete wall 10 according to the invention, thefirst concrete layer 13 a contains at least 0.05 mass % boron-10 isotopewith respect to the concrete forming the concrete layer 13 a, and thesecond concrete layer 13 b is formed as heavyweight concrete. It shouldbe noted that the characteristic isotope composition of elemental boron(expressed in mole fraction) is 0.199(7) boron-10 isotope and 0.801(7)boron-11 isotope, as is known to a person skilled in the art, thereforeboron-10 isotope is present both in the elemental boron and the boroncompounds as well. In a preferred embodiment the boron-10 isotope ispresent in the first concrete layer 13 a in the form of a boroncompound, preferably boron carbide (B₄C). Boron carbide is used widelyin industry for other purposes (such as an abrasive). As a consequenceof the physical properties of boron carbide, it is suitable forreplacing at least some of the sand used during concrete production, inother words it may be used to produce a high boron content concrete.Embodiments are also conceivable in the case of which the concentrationdistribution of the boron-10 isotope in the first concrete layer 13 a isnot homogenous. As the neutron radiation arrives at the surface 11 a,and the slow neutrons do not penetrate deeply into the concrete, in thecase of a possible embodiment the concentration of the boron-10 isotopeis greater closer to the surface 11 a, and the concentration of theboron-10 isotope decreases with distance from the surface 11 a towardsthe surface 11 b. The concentration may change continuously, for examplebetween a maximum mass % value and 0 mass %, or even in steps. In thecase of a preferred embodiment, the thickness of the first concretelayer 13 a is approximately 5 cm.

In the case of a possible exemplary embodiment the concrete layer 13 acontains 71.621 mass % sand and gravel, 0.329 mass % boron carbide, 18.7mass % Portland cement and 9.35 mass % water. Naturally, other concretecompositions are conceivable, as is known to a person skilled in theart.

The second concrete layer 13 b is formed as heavyweight concrete. In thecontext of the present invention, heavyweight concrete is understood tomean a concrete known to a person skilled in the art containing iron(e.g. crushed iron ore, iron ore powder, compound containing iron, orsteel shot, etc.), and other heavy elements, such as barium, lead orcopper. In the case of a possible exemplary embodiment, the concretelayer 13 b contains 42 mass % hematite, 44.5 mass % steel shot, 8 mass %Portland cement, 5.3 mass % water and 0.2 mass % retarder. It should benoted that, optionally, naturally other heavyweight concretecompositions are conceivable, as is obvious for a person skilled in theart. The thickness of the concrete layer 13 b is preferably between 5 cmand 2 m depending on the radiation source 12 and the intensity of theneutron radiation.

In the case of a possible embodiment the first and/or the secondconcrete layer 13 a, 13 b contain reinforcing mesh 15, and the first andsecond concrete layers 13 a, 13 b are fixed to each other with thereinforcing mesh 15, as it can be seen in FIG. 2. In this case a part ofthe reinforcing mesh 15 is located in the concrete layer 13 a, andanother part of it is located in the concrete layer 13 b. Thereinforcing mesh 15 also provides further structural stability to theconcrete layers 13 a, 13 b by increasing tensile strength.

In the case of another possible embodiment, the first and secondconcrete layers 13 a, 13 b are formed as separate layers fixed to oneanother. The fixing of the concrete layers 13 a, 13 b to each other maytake place with known fixing elements, such as with bolts 17, as isshown in FIG. 3. The concrete layers 13 a, 13 b may also optionallycontain reinforcing meshes 15.

The object of the invention also relates to a concrete wall 10, whichcontains heavyweight concrete containing at least 0.05 mass % boron-10isotope (¹⁰B). The concrete wall 10 may also contain additional layers(e.g. a lightweight concrete layer), but preferably the concrete wall 10contains a single concrete layer formed as heavyweight concretecontaining at least 0.05 mass % boron-10 isotope. In the case of apossible embodiment, the distribution of the boron-10 isotope in theheavyweight concrete is even. In the case of a preferred embodiment thedistribution of the boron-10 isotope in the heavyweight concrete is suchthat it is present in a concentration that increases towards the side ofthe heavyweight concrete facing the radiation source 12, in other wordsthe concentration of the boron-10 isotope is at a maximum at the side ofthe heavyweight concrete facing the radiation source 12, and at aminimum at the side opposite it, optionally 0 mass %. It should be notedthat in the case of this embodiment also, the concrete wall 10 may alsocontain reinforcing mesh 15 in order to increase structural stability.

The object of the invention also relates to a method for the productionof a concrete wall 10 for absorbing neutron radiation, which has aninternal delimiting surface 11 a, and an external delimiting surface 11b on an opposite side to the internal delimiting surface 11 a. Duringthe method according to the invention a first concrete layer 13 acontaining at least 0.05 mass % boron-10 isotope is formed on the sideof the internal delimiting surface 11 a, and a second concrete layer 13b formed as heavyweight concrete is created on the side of the externaldelimiting surface 11 b.

In the case of a particularly preferred embodiment of the method, aconcrete wall 10 containing the concrete layers 13 a, 13 b as a singleconcrete block is created as follows. Liquid phase heavyweight concrete13 b′ is filled into the lower part of the concrete casting mould 20, asit may be seen in FIG. 4a , for example. The casting mould 20 isselected in accordance with the concrete wall 10 to be built; in thisway various surfaces (e.g. planar, curved, arched, bent, etc.) can becreated. Therefore the casting mould 20 may be, for example, the openedtop casting mould illustrated in FIGS. 4a to 5b , but, optionally, itmay also be a closed casting mould 20 enclosed from all sides (notillustrated in the figures), as is known to a person skilled in the art.The advantage of the closed casting mould 20 is that it may use toproduce concrete layers 13 a, 13 b of practically any desired shape ofsurface (arched, curved, etc.).

In the second step of the method, before the heavyweight concrete 13 b′starts to bond, liquid phase concrete 13 a′ containing at least 0.05mass % boron-10 isotope is poured into the casting mould 20 (see FIG. 4b). In this way the liquid phase concrete 13 a′ and heavyweight concrete13 b′ bond practically simultaneously as a single concrete block, withcement bonding (hydraulic bonding) being created between the concretelayers 13 a, 13 b. After bonding, the second concrete layer 13 b isformed from the liquid phase heavyweight concrete 13 b′, and the firstconcrete layer 13 a is formed from the liquid phase concrete 13 a′containing at least 0.05 mass % boron-10 isotope. It should be notedthat an embodiment is also conceivable (not illustrated in the figures)in the case of which first the liquid phase concrete 13 a′ containing atleast 0.05 mass % boron-10 isotope is filled into the lower part of thecasting mould 20, then liquid phase heavyweight concrete 13 b′ is pouredonto the top of the liquid phase concrete 13 a′ containing at least 0.05mass % boron-10 isotope. As the concrete 13 a′ and the heavyweightconcrete 13 b′ come into contact with each other in the liquid phase,they may penetrate into each other to a certain extent during bonding,therefor the layer border 14 will not be well defined in a given case.In practice, however, this does not cause any problem.

In the case of another preferred embodiment of the method according tothe invention, the mixing of the layers is reduced by only pouring theliquid phase concrete 13 a′ containing at least 0.05 mass % boron-10isotope or the liquid phase heavyweight concrete 13 b′ after the liquidphase heavyweight concrete 13 b′ or the liquid phase concrete 13 a′containing at least 0.05 mass % boron-10 isotope filled into the lowerpart of the casting mould 20 has partially bonded.

In the case of another preferred embodiment a reinforcing mesh 15 isplaced in the liquid phase heavyweight concrete 13 b′ or the liquidphase concrete 13 a′ containing at least 0.05 mass % boron-10 isotopefilled into the casting mould 20, which reinforcing mesh 15 passesthrough the surface of the liquid phase heavyweight concrete 13 b′ orthe liquid phase concrete 13 a′ and which remains partially uncovered,as is shown in FIG. 5a , for example. The reinforcing mesh 15 may beinstalled before, during or after the heavyweight concrete 13 b′ or theconcrete 13 a′ is filled into the casting mould 20, up until it bonds.After the liquid phase heavyweight concrete 13 b′ or the liquid phaseconcrete 13 a′ containing at least 0.05 mass % boron-10 isotopecompletely or partially bonds, liquid phase heavyweight concrete 13 b′or liquid phase concrete 13 a′ containing at least 0.05 mass % boron-10isotope is poured onto the surface determining the layer boundary 14,onto the partially uncovered reinforcing mesh 15 (see FIG. 5b ). In thecase of this embodiment, the bonding between the concrete layers 13 a,13 b is not only provided by the cement bond, but also by thereinforcing mesh 15. In this case the layer poured first maysignificantly solidify before the second layer is poured.

In the case of another preferred embodiment of the method according tothe invention the first and second concrete layers are createdseparately (e.g. in separate casting moulds 20 or in the same castingmould 20 at different times), then the first and second concrete layers13 a, 13 b are fixed to each other using fixing devices known to aperson skilled in the art, such as bolts 17 (see FIG. 3). In this casecare has to be taken that the surfaces of the concrete layers 13 a, 13 bfacing the layer boundary 14 fit to each other. This may be solved usingappropriately selected casting moulds 20. It should be noted that theseparately poured concrete layers 13 a, 13 b may also optionally containreinforcing mesh 15 in order to increase structural stability.

Various modifications to the above disclosed embodiments will beapparent to a person skilled in the art without departing from the scopeof protection determined by the attached claims.

1. Neutron absorbing concrete wall (10), having an internal delimitingsurface (11 a), and an external delimiting surface (11 b) on an oppositeside to the internal delimiting surface (11 a), characterised by a firstconcrete layer (13 a) on the side of the internal delimiting surface (11a), and a second concrete layer (13 b) on the side of the externaldelimiting surface (11 b), wherein the first concrete layer (13 a)contains at least 0.05 mass % boron-10 isotope (¹⁰B), and the secondconcrete layer (13 b) is heavyweight concrete.
 2. Concrete wall (10)according to claim 1, characterised by that in the first concrete layer(13 a), boron-10 isotope is contained in boron carbide.
 3. Concrete wall(10) according to claim 1, characterised by that in the first concretelayer (13 a) the boron-10 isotope is present in a concentration thatincreases towards the internal surface (11 a).
 4. Concrete wall (10)according to claim 1, characterised by that the thickness of the firstconcrete layer (13 a) is a maximum of 5 cm.
 5. Concrete wall (10)according to claim 1, characterised by that the second concrete layer(13 b) contains a member of the group consisting of iron, lead, copper,barium, and combinations thereof.
 6. Concrete wall (10) according toclaim 1, characterised by that the first and second concrete layers (13a, 13 b) are a single cast block.
 7. Concrete wall (10) according toclaim 1, characterised by that the first and second concrete layers (13a, 13 b) are separate layers secured to each other.
 8. Concrete wall(10) according to claim 1, characterised by that at least one of theconcrete layers (13 a, 13 b) contains a reinforcing mesh (15), and theconcrete layers (13 a, 13 b) are secured to each other with thereinforcing mesh (15).
 9. Method for creating a neutron radiationabsorbing concrete wall (10) that has an internal delimiting surface (11a), and an external delimiting surface (11 b) on an opposite side to theinternal delimiting surface (11 a), characterised by forming a firstconcrete layer (13 a) as concrete containing at least 0.05 mass %boron-10 isotope (¹⁰B) on the side of the internal delimiting surface(11 a), and forming a second concrete layer (13 b) as heavyweightconcrete on the side of the external delimiting surface (11 b). 10.Method according to claim 9, characterised by pouring liquid phaseheavyweight concrete (13 b′) into a lower part of a casting mould (20),then pouring liquid phase concrete (13 a′) containing at least 0.05 mass% boron-10 isotope (¹⁰B) into the casting mould (20) on top of liquidphase heavyweight concrete (13 b′).
 11. Method according to claim 10,characterised by pouring the liquid phase concrete (13 a′) containing atleast 0.05 mass % boron-10 isotope (¹⁰B) on top of the liquid phaseheavyweight concrete (13 b′) only after the liquid phase heavyweightconcrete has partially bonded.
 12. Method according to claim 10,characterised by placing a reinforcing mesh (15) in the liquid phaseheavyweight concrete (13 b′) filled into the casting mould (20), whichreinforcing mesh (15) passes through the surface of the liquid phaseheavyweight concrete (13 b′) and remains partially uncovered, and afterat least partial bonding of the liquid phase heavyweight concrete (13b′) pouring on the partially uncovered reinforcing mesh (15) liquidphase concrete (13 a′) containing at least 0.05 mass % boron-10 isotope(¹⁰B).
 13. Method according to claim 9, characterised by creating thefirst and second concrete layers (13 a, 13 b) separately, then securingthe first and second concrete layers (13 a, 13 b) to each other. 14.Method according to claim 9, characterised by providing a reinforcingmesh (15) in at least one of the concrete layers (13 a, 13 b). 15.Neutron absorbing concrete wall (10), characterised by heavyweightconcrete containing at least 0.05 mass % boron-10 isotope (¹⁰B). 16.Method according to claim 9, characterized by pouring liquid phaseconcrete (13 a′) containing at least 0.05 mass % boron-10 isotope (¹⁰B)into a lower part of the casting mould (20), then pouring liquid phaseheavyweight concrete (13 b′) on top of liquid phase concrete (13 a′)containing at least 0.05 mass % boron-10 isotope (¹⁰B); creating afterbonding a second concrete layer (13 b) from the liquid state heavyweightconcrete (13 b′) and a first concrete layer (13 a) from liquid phaseconcrete (13 a′) containing at least 0.05 mass % boron-10 isotope (¹⁰B).17. Method according to claim 16, characterized by pouring liquid phaseheavyweight concrete (13 b′) on top of the liquid phase concrete (13 a′)containing at least 0.05 mass % boron-10 isotope (¹⁰B) only after theliquid phase concrete has partially bonded.
 18. Method according toclaim 16, characterized by placing a reinforcing mesh (15) in the liquidphase concrete (13 a′) containing at least 0.05 mass % boron-10 isotope(¹⁰B) filled into the casting mould (20) which reinforcing mesh passesthrough the surface of the liquid phase concrete (13 a′) and remainspartially uncovered, and after at least partial bonding of the liquidphase concrete (13 a′) containing at least 0.05 mass % boron-10 isotope(¹⁰B) pouring on the partially uncovered reinforcing mesh (15) liquidphase heavyweight concrete (13 b′).